Rolls-Royce (R-R) is developing continuous improvements for mature Trent engines, with new technology flowing from later models into established variants, according to program director John Hogarth. Since the original Trent–the Series700–entered service on a Cathay Pacific Airbus A330 in 1985, successive variants have been introduced to constitute a “tailored family” enjoying common architecture, but with each model dedicated to specific airframes.
The manufacturer has established a suite of “enhanced performance” (EP) developments that improve production standards or which can be applied retrospectively to upgrade early examples of each Trent family member. EP improvements have been developed for the Trent 500 (which powers the Airbus A340-500), Trent 700 (A330), and Trent 800 (Boeing 777), with two standards available for the Airbus A380’s Trent 900 engines.
The Trent is derived from the RB211 (developed for the Lockheed L-1011 TriStar during the 1970s and which famously pushed Rolls-Royce into receivership), the initial Trent 600 having been based on the RB211-524L that was intended for the Boeing 767-400ERX (that never entered production) and which was offered as a competitor against Pratt & Whitney PW4000 or General Electric CF6 engines for the McDonnell Douglas MD-11.
Technology feedback started from the Trent 700, which produced upgrades for the RB211-535 and “most” older -524G/H engines that powered the Boeing 757 and 747, respectively. A trend was soon established that has seen the Trent 700 benefit from both Trent 800 and Trent 1000 development, while technology from the Trent 900 has been applied to the Trent 500 and the new Airbus A350’s Trent XWB is feeding into the Trent 1000.
A good example of this technology feedback arises from Trent 1000 “elliptical leading-edge” (ELE) high- and intermediate-pressure compressor (HPC and IPC) blades, which reduce fuel burn and are now available for Trent 800 EP and Trent 500EP+ applications. Hogarth said the blade's “sophisticated aerodynamics,” which reduces airflow separation behind the leading edge, provides a 0.5- to 0.7-percent benefit to fuel consumption worth “up to $200,000 per aircraft per year.” First customer orders have been agreed, perhaps for announcement here at Le Bourget.
Trent 700 fuel burn is said to have benefitted by 1.1 percent from an EP retrofit package introduced in 2009, with an “EP2” expected to follow in two years’ time, although RR does not yet know if this will be available for retrofit. The initial Trent 700 EP retrofit kit includes ELE IPC/HPC blades and optimized turbine-case cooling. These changes are available on new-build engines, along with other developments such as optimized blade-tip clearance, “pocket-less” fan-spinner fairing, “super-polished” turbine hardware, and HPC improvements that together give new engines a 1.3 percent fuel-efficiency gain.
Planned Trent 700 EP2 characteristics that will lead to a new 2015 build standard and which could yield one-percent fuel-burn improvements (worth $200,000 per aircraft per year) include HPC and IPC stator-blade changes, better nozzle guide-vane (NGV) sealing and an improved “aero-standard flutter bridge” in the low-pressure turbine (LPT). As Airbus A330 popularity continues, the engine manufacturer is producing “more [Trent 700s] than ever before.”
R-R (Chalet B89) said last month that an EP2 package would run this year, following an initial EP upgrade that improved fuel burn and enhanced engine reliability. “Delays and cancellations and unscheduled engine-removal rates have improved by 50 percent in the past two years,” according to Hogarth. The Trent 900 EP2 includes further optimization of turbine case cooling (benefiting from Trent XWB technology), and an optimized air system that contribute to a “further 0.5- to 0.8-percent” fuel-burn improvement over the gains generated in the earlier EP.
The Trent 900 EP “Block 1” standard performance upgrade covers ELE blades, tighter LPT blade-tip clearance, and a hard coating on the HPC drum to allow closing running of stator blades. A long list of “maturity” improvements includes HP and intermediate-pressure (IP) turbine disc and blade changes, an LP location bearing package, work on IP NGVs, and an upgraded electronic engine control software package.
R-R’s Trent 500EP was introduced on new-build engines and offered a one-percent fuel-efficiency improvement. A planned EP+ upgrade for the Trent 500, which at 127 aircraft comprises the company's second-largest Trent fleet, is expected to provide a further 0.5-percent gain. The Trent 500EP+ was scheduled to enter testing in mid-2013, a year ahead of entry-into-service, and will be offered as a retrofit package.